Alzheimer?s Disease-Related Administrative Supplement to DP1 DA041722 under NOT-AG-18-039 PROJECT SUMMARY Alzheimer?s disease (AD) prevalence is increasing and already affects over 5% of those over age 65. While AD manifests amyloid plaques and tau tangles, loss of synapses and neurons more closely correlates with cognitive decline. Damage to neurons occurs at least partially through generation of oxidative and nitrosative stress, due to excessive generation of reactive oxygen/nitrogen species (ROS/RNS) triggered in part by oligomeric amyloid-? (A?) peptide. Our group has shown that a predominant reaction in this regard is aberrant S-nitrosylation of critical cysteine residues that affect protein function/activity. In a prior year?s supplement, we used our innovative Mass Spectrometry (MS) platform to elucidate the S-nitrosoproteome in postmortem human AD brain similar to the parent grant looking at HIV-associated neurocognitive disorder (HAND) and HAND/methamphetamine exposed human brains. In Preliminary Studies, we have shown that S-nitrosylation of a network of proteins in AD and HAND/meth may contribute to synaptic damage and loss. Strikingly, we found, among other pathways, that the TCA cycle displays multiple aberrant S- ntrosylated enzymes, disrupting its function. We now propose in this supplement to model these findings in AD hiPSC-patient derived neuronal cultures and cerebral organoids in order to test small molecules that might be able to treat the resulting loss of ATP/bioenergetic supply and resulting neuronal and synaptic injury. This model system would be performed in parallel to work being performed in the parent grant on HIV/meth exposed hiPSC-derived neurons. Hence, the new proposed studies on hiPSC-derived neurons and cerebral organoids are within the scope of the parent project. Accordingly, we propose the following Specific Aims: Aim 1: To determine the S-nitrosoproteome, specifically with regard to its aberrant inhibition of TCA cycle enzymes, in human AD hiPSC neuronal cultures and cerebral organoids, and compare/contrast the pathways involved to those encountered in HIV-associated neurocognitive disorder (HAND) and HAND with methamphetamine abuse in both human brain cortex and hiPSC-derived neurons. Aim 2: To test small molecules related to succinate for their ability to bypass steps in the TCA cycle inhibited by aberrant S-nitrosylation in order to rescue energy compromised and consequent neuronal damage in AD hiPSC neuronal cultures and cerebral organoids.